As a background art of the present technical field, there is cited Japanese Patent Laid-Open No. 2009-236520 (Patent Literature 1). This publication indicates that “at a time of deviating from a guide route (S39), a plurality of routes from the present location to the destination are searched for (S42), and a driver is caused to select one of the plurality of routes as a guide route. When the guide route is decided by selection of a user (S44), guidance to the destination is started based on the guide route (S47). During travel without deviating from the guide route, other search routes than the search route of the guide route, and further route selection buttons are displayed, as well as the search route of the guide route on the map, on the screen of a touch screen type display unit 27 (S48). In each of the selection buttons, information on a required distance, a required time period and the like for a corresponding route is displayed. When the driver presses the selection button (S49), the guide route is changed to the route of the selection button, and thereafter, route guidance is returned to (S47).”.